Field
The following description relates generally to wireless network communications, and more particularly to carrier aggregation.
Background
Wireless communication systems are widely deployed to provide various types of communication content such as, for example, voice, data, and so on. Typical wireless communication systems may be multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, . . . ). Examples of such multiple-access systems may include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and the like. Additionally, the systems can conform to specifications such as third generation partnership project (3GPP) (e.g., 3GPP LTE (Long Term Evolution)/LTE-Advanced), ultra mobile broadband (UMB), evolution data optimized (EV-DO), etc.
Generally, wireless multiple-access communication systems may simultaneously support communication for multiple mobile user equipment (UE). Each UE may communicate with one or more evolved Node B (eNB) via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from eNB to UE, and the reverse link (or uplink) refers to the communication link from UE to eNB. Further, communications between UE and eNB may be established via single-input single-output (SISO) systems, multiple-input single-output (MISO) systems, multiple-input multiple-output (MIMO) systems, and so forth.
UEs can communicate with eNBs using one or more radio access technologies (RAT), such as LTE, high speed packet access (HSPA), universal mobile telecommunication system (UMTS), and/or similar technologies or variants thereof. Some UEs can switch among RATs when communicating with given base stations to achieve diversity in network operability. In addition, carrier aggregation (CA) is developing to allow a UE to communicate with one or more eNBs over one or more component carriers (CC). This can improve throughput at the UE and/or allow the UE to receive multiple simultaneous services from various nodes. In one CA scheme, a UE can establish carriers with multiple serving cells, and can have a primary CC (PCC) with an eNB or related cell, which can be referred to as the primary cell (PCell), and one or more secondary CCs (SCC) with the same or other eNBs or cells, which can be referred to as secondary cells (SCell). The PCC or PCell can be used for communicating control data related to all CCs.